The present invention relates to a method for the detectable release of gas which is stored in the interior of a first container into the interior of a second container which is sealed from the exterior and to an apparatus for implementing the method.
A particular problem exists when checking containers for leaks by means of a helium leak test or when starting up chemical reactions by the defined release of one or a plurality of the reaction partners in a container that is sealed externally if this container has no passages or openings in its interior, for example for the purpose of manipulating devices disposed in sealed containers. Each actuating mechanism involved, e.g., valves, must then act through a completely sealed wall, so that the actuation signals for these mechanisms must be thermal or electromagnetic signals. However, these types of signals do not permit any conclusion as to whether or not the desired effect has been realized within the container whose interior cannot be visually observed.
Leakage tests of containers with the aid of a helium leak test are disclosed in detail in various textbooks, e.g., Wutz, Adam, Walcher, "Theorie und Praxis der Vacuum-technik" (Theory and Practice of Vacuum Technology) (1982), or pages 10.3 and 10.4 of the catalog of Leybold. In this process, either the container to be tested is placed into a pressure chamber filled with helium and the quantity of helium which penetrated into the container itself is measured, or the container interior is charged with helium, is placed into a vacuum chamber and the quantity of helium escaping from the container is measured.
Another method is the so-called "bombing" method, wherein the sealed container is placed into a pressure chamber and is kept in the helium atmosphere under pressure for a longer period of time. Then the pressure chamber is evacuated, and thereafter the helium escaping from the container is measured. From the measured values, a conclusion can then be drawn as to the leakage of the container.
Another method is the use of a cartridge which has a defined helium leakage through a defined capillary tube. This cartridge is placed into the container before the latter is sealed and then very slowly loses its helium content. Thereafter, the container is placed into a vacuum chamber and the quantity of helium leaving the container is measured. Alternatively, a valve disposed in a cavity can be connected to the container through which valve the container is filled with helium. The above-mentioned cavity is sealed against the environment by means of a plug or a closing screw and is additionally sealed by a welded seam.
These pressure and vacuum processes require a connection with the container which, upon completion of the leakage test, must again be sealed and again separately checked. This procedure is very complicated, particularly when checking containers having a radioactive content since, in such case, all manipulations, e.g. welding or unscrewing of fill or discharge pipes, must here be effected by remote control.
The "bombing" method has the drawback of not being very accurate (up to 10.sup.-4 mbar l/s). Moreover, the release of helium from a defined capillary tube has the drawback that, considering the possible leakage of the container and its detectability, a large quantity of helium must be introduced into the container which then, if the container is perfectly tight, results in a relatively great increase in pressure in the container.